As is known, a photocathode is a negatively charged electrode in a light detection device, such as a phototube or photomultiplier. The electrode is coated with a photosensitive material, such that when light impinges on the photosensitive material, the absorbed energy causes electron emission due to the photoelectric effect. Current photocathode designs are typically planar and have not structurally changed since the early phototubes.
Photo-emissive devices generally have limited quantum efficiency due to a number of non-trivial issues.